Siemens MJ-4A Installation And Operation Manual page 57

NEUT R (Neutral Reverse)
This mode of operation is intended for use on systems
where reverse power flow is an abnormal situation.
In this mode, the controller always operates in the forward
mode. When current magnitude drops below the forward I
Threshold % setpoint, tap changes are inhibited. When
the reverse current magnitude exceeds I Threshold % set-
point for ten seconds, the tap changer resumes operation
and returns the tap changer to the neutral position without
stopping. The tap changer then remains at the neutral
position until forward current magnitude once again
exceeds the I Threshold % setpoint.
If, while the tap changer is returning to neutral, the for-
ward current magnitude increases above the I Threshold
% setpoint, normal forward tap changer operation
resumes.
Neutral Reverse mode is dependent upon the MJ-4 tap
tracking algorithm. If the tap position is unknown to the
microprocessor, the tap changer idles at the last held posi-
tion.
View Pwr Flow: NEUT R on the <CONFIGURE> Menu.
Reverse Current
Return to
Tap Changes Inhibited
neutral
after ten
seconds
Continue return
to neutral
RPF indicator on
Band indicators flashing
I
Threshold % 1%
Current
Neutral Reverse Mode
Figure 6.6
Siemens Energy, Inc.
6
MJ-4A & MJ-4B Control Panel Automatic Mode
Forward Current
Forward
Operation
RPF indicator off
Band indicator
LEDs on
I
0 1% Threshold %
CO-GEN (Co-generation)
This mode of operation is for use on systems where
power flows from Utility to consumer at certain times and
from consumer to Utility at other times. In this mode, the
tap changer operates whenever current magnitude (either
forward or reverse) exceeds the I Threshold % setpoint.
In this mode, the controller always operates in Forward
mode. Forward Line Drop Compensation values are used
when forward current magnitude exceeds the I Threshold
% setpoint. Reverse Line Drop Compensation values are
used when reverse current magnitude exceeds the I
Threshold % setpoint. Tap changes are inhibited when
current magnitude is between the I Threshold % set-
points.
View Pwr Flow: CO-GEN on the <CONFIGURE> Menu.
Reverse Current
Forward
Tap Changes Inhibited
Operation
with
Reverse
LDC
RPF indicator on
Band indicators flashing
I
Threshold % 1%
Current
Figure 6.7 Co-generation Mode
Forward Current
Forward
Operation
with
Forward
LDC
RPF indicator off
I
0 1% Threshold %
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